1. Technical Field
The present invention relates to a retainer, a deep-groove ball bearing, and a sealed bearing.
2. Background Art
As illustrated in FIG. 15, the bearing (deep-groove ball bearing) includes an outer race 2 having a circular-arc outer raceway surface 1 formed on an inner periphery thereof, an inner race 4 having a circular-arc inner raceway surface 3 formed on an outer periphery thereof to face the outer raceway surface 1, a retainer 5 arranged between the inner race 4 and the outer race 2, and a plurality of balls Bo rollably supported by the retainer 5.
As illustrated in FIG. 16, the retainer 5 is formed by combination of two annular retaining plates 7 and 7 each including semispherical swelling portions 6 arranged at predetermined intervals along a circumferential direction. Specifically, each of the annular retaining plates 7 includes the semispherical swelling portions 6 arranged along the circumferential direction and flat portions 8 between the semispherical swelling portions 6 adjacent to each other. In a combined state, the flat portions 8 and 8 are superimposed on each other, and the flat portions 8 and 8 are coupled to each other through intermediation of fasteners 9 such as rivets. Thus, the semispherical swelling portions 6 face each other to form ring-shaped ball-fitting portions (pockets) 10.
Conventionally, there has been provided a bearing in which a lubrication state of the retainer and the balls (Patent Literature 1) is improved, a bearing in which a lubricating oil is positively fed and discharged so that fluidity of the lubricating oil in the bearing is enhanced (Patent Literature 2), or the like.
The bearing described in Patent Literature 1 includes support recessed portions provided on inner peripheral sides of each of the pockets, the support recessed portions being made to function as lubricant pools for storing lubricant. With this, a retaining amount of the lubricant in the pockets is increased so that the lubrication state of the retainer and the balls is improved.
Further, the bearing described in Patent Literature 2 similarly includes recessed portions formed on inner peripheral surfaces of each of the pockets. The recessed portions respectively communicate to a bearing space side between the outer race and the retainer and to a bearing space side between the inner race and the retainer so that lubricating oil paths having recessed-groove shape are formed.
By the way, foreign matter such as abrasion powder of gears is mixed in an automobile transmission. Thus, a conventional bearing used for an automobile transmission is a sealed bearing including contact-type seal members for sealing a bearing space formed between the inner and outer races thereof. With this structure, foreign matter is prevented from intruding into the bearing.
When the bearing space is sealed with the contact-type seal members, foreign matter is prevented from intruding into the bearing. However, large seal torque of the seal members constitutes a problem with improvement of fuel efficiency of automobiles. As the sealed bearing, there has been proposed one of a type that the seal torque is reduced (for example, Patent Literature 3). In the sealed bearing described in Patent Literature 3, shot peening is performed on a surface with which a seal lip portion comes into sliding contact, for example, on an inner wall surface of a seal groove of a bearing rotating race. In this manner, a maximum roughness Ry of the contact surface is set to be small, specifically, 2.5 μm or less. With this, the seal torque is reduced.